Yep, it will be interesting to see – Apple Watch can already monitor for atrial fibrillation:
https://support.apple.com/en-gb/HT212214. Though, it looks like the patient must already have a diagnosis from a doctor. So rather than diagnosing, it's sort of an AF tracker - which is useful as AF can come and go.
The problem obviously with heart attacks is the implications of false negatives and positives are huge, and the tracing from a watch would be less reliable than the gold-standard ECG / EKG.